The present invention relates generally to a cable, such as a downhole electrical power cable, designed to protect the conductive inner core, to allow the easy removal of corroded or damaged armor, and to facilitate the cost effective replacement of the armor and reuse of the cable core.
In a variety of applications, it is necessary to use an armored electrical power cable in a hostile environment. For example, in subsurface production of liquids, such as oil, it may be necessary to provide electrical power to an electric submersible pumping system located deep underground. Typically, a power cable is run downhole and connected to a submersible electric motor. The electric motor is powered to turn a centrifugal pump that intakes the production fluid and raises it or moves it to a desired location, such as the surface of the earth.
In such applications, the electric submersible pumping system often is utilized within a wellbore at a location deep beneath the surface of the earth. In that type of environment, components are subjected to extreme pressures and often to corrosive environments. Thus, it can be difficult to protect the vital inner components of the power cable core and to maintain the integrity of its outer layers.
In conventional downhole electrical power cables, there is an inner core of copper conductors encased in high dielectric insulation, a barrier layer, and a rubber jacket. A layer of armor typically composed of galvanized steel, stainless steel, or Monel protects this inner core. The downhole electrical power cable is reused until such time as the armor is corroded or damaged or until the cable conductors short out.
When the layer of armor is damaged the cable is either repaired in sections, scrapped or stripped down to recover the copper conductors. The bulk of galvanized armor scrapped in the field is due to corroded or rusted armor which usually causes varying degrees of surface damage to the jacket. While the damaged armor can be replaced in the field, the damaged surfaces of the rubber jacket often will not allow proper wrapping of the armor on the cable due to surface unevenness. If the cable is not repaired for reuse, the armor, jacket, and insulation are stripped away to recover the copper conductor which is resold to the cable manufacturer.
It would be advantageous to create a relatively simple cable which would allow repair and reuse of the cable on a routine basis.
The present invention features a resheathable cable armor system. The system includes a sacrificial insulation jacket over the current inner core. This sacrificial inner jacket is in addition to the current insulation system. Therefore it can be removed without compromising the original insulation capacity.
According to another aspect of the invention, the cable is designed with a rip cord or cords disposed longitudinally along its length. Pulling the ripcord or cords slits through the sacrificial jacket and armor layer without undermining the integrity of the inner core and allows the easy removal of the sacrificial jacket and armor layer. A field usable armor installation machine can then be used in the field to re-armor the used cable, allowing its reuse. This gives the cable a minimum of two uses in the field before it is scrapped or salvaged.